/*
 * Copyright (c) 2008-2019, Hazelcast, Inc. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.hazelcast.internal.cluster;

public interface ClusterClock {

    /**
     * Returns the cluster-time in milliseconds.
     * The cluster-time measures elapsed time since the cluster was created. Comparable to the {@link System#nanoTime()}.
     * @return the cluster-time (elapsed milliseconds since the cluster was created).
     */
    long getClusterTime();

    /**
     * Returns the cluster  up-time in milliseconds.
     * When first node in cluster becomes master, its clusterTime value is saved as
     * clusterStartTime. Up-time of cluster is calculated as
     * ClusterClock#getClusterTime - clusterStartTime.
     *
     * @return the cluster-up-time
     */
     long getClusterUpTime();
}
